Variable diameter and variable pitch propeller



July 16, 1946. w. s. HOOVER VARIABLE DIAMETER AND VARIABLE PITCH PROPELLER Filed March 14, 1941' 6 Sheets-Sheet 1 INVENTCR. v m s. fi e Ma y 1946. w s. HCQVER 2,4643% VARIABLE DIAMETER AND VARIABLE .PII'CH PROPELLER Filed March 14, 1941 6 Sheets-Sheet 2 Iii/g. 3

I INVENTOR. m s. W

' July 16, 1946. w. s. HOOVER' 2,404,290

VARIABLE DIAMETER AND VARIABLE PITCH PROPELLER Filed March 14, 1941 Sheets-Sheet 3 INVENTOR. W m/1 s W BY W July 16, 1946. HOOVER 2,404,290

VARIABLE DIAMETER AND VARIABLE PITCH PROPELL ER J Filed March 14, 1941 6 Sheets-Sheet 4 INVENTOR. m 5. W

BY I 6W y v194(5- I w. s. HOOVER 2,404,290

VARIABLE DIAMETER AND VARIABLE PITCH PROPELLER Filed March 14, 1941 e- Sheets-Sheet s July 16, 1946. w. s. HOOVER VARIABLE DIAMETER AND VARIABLE PITCH PROPELLER :Filed March 14, 1941 s Sheets-Sheet 6 INVENTOR. 74% 5. MW

Patented Jul 16, 1946 VARIABLE DIAMETER ANDVARIABLE PITCH PROPELLER Walter S. Hoover, Montreal, Quebec,.Canada. Application March 1 4, 194 1, S'erial'No; 383,389

13 Claims. 1

the invention is. the provision of pitch adjusting means for variable diameter propellers. with means for coordinating the pitchadjusting means and variable diameter adjusting means.

By the use of variable diameter propellers-or variable pitch propellers, itispossible to obtain constant engine speed. through flywei'ght governor control because in either case variations of the propeller thrust result in variations ofthe load on the motor;

If the engine speeds tendrto increase above normal, increase in. propeller. thrust, by increasing the diameter or totalthrust area, or by increasing the pitch setting of the. blades, will maintain the engine speed. constant.

Also, if. in climbing or due. to change in wind velocity the load. on the engine increases tend.- ing to reduce the engine speed,,a decrease of the propeller thrust area by reducing the diameter of the blades, or by decreasing the pitch setting. will maintain the speed of the motor constant.

The present invention, contemplates the use. ofeither or both of these expedients for maintaining constant engine speed. The invention will become more apparent from a consideration of the accompanying. drawings constituting a part hereof in which like reference characters designate like parts andin which:

Fig. 1. is a view partially insection andpartially in side elevation of a variable diameter propeller unit with means for varying, the pitch setting of the propeller blades;

Fig. 2 a front elevational' view thereof;

Fig. 3 a cross-sectional view taken alongthe line 3-3, Fig. 1;

Fig. 4 a sectional view taken. along the line L-d, Fig. 1;

Fig. 5 a crossesectional view partially in side elevation of the propeller unit shown inIig. 1;

Fig. 6 a cross-sectional view partially in side elevation of a modified form of. variable pitch propeller mechanism;

Fig. 7 a vertical crossrsectional view of, a governor control unit;

Figs. 8 and 9 diagrammatic views illustrating the application offluid pressure to the hy draulic actuator;

Fig. 10 aview in perspective of a manual. control lever and Fig. ILatdiagrammatic View of a governor controlled. servo mechanism.

With. reference to. Fig. IV of the drawings, the

valve structurev therein illustratedcomprises. the frontor nose end-of the engine designated by the refer.- ence numeral I. having a governor unit Zrespon-g sive to the speed. of. the motor mounted thereon, the crankshaft-'3. of. theeng'ine' terminating in a flange to which is. connected the propeller hubunit generally designated by the reference character The hub unit is mounted for selfcentering on. a rubber ring 5 and is 'attachedto' the engineshaft 3' by suitable'b'olts, notshown,

The pitch setting of the blades is effected through. amaster gear 6 that interacts with the teeth of the end gear 7 which carries the" blade retainer. Theblade-rootsd are mounted inthe blade retainer- 9- by engagement" of their buttress threads H], and the blade retainer ismovable about its own axis by interlocking engagement of ball bearings H which are disposed. in" angularly spaced vertical slots H2, or which there are 5 around the blade retainer 9: and in: thecomplementaryslots of the bladeend gear sleeve la. The ball bearings-are yieldingly mounted in slots iZ-bysprings [2a- Variation in diameteris permitted by the inward and outward motion of the bladerretainer il-in the blade gearsleeve 1w aided by the-bearing surfaces of the ball bearings l I: l

The propeller hub- 4 is provided with radially extending. armss l-3ihaving a piston I4 on the extended ends thereof, the piston being" counterbored' at t5 to form an oil chamber with the transversewall l6-of the blade retainer 9, the piston I l-being spaced from the'base I! of the blade retainer sit!) form a fluid chamber. By the routing of fluid under pressure into the fluid. chambers above'or' below the piston M the'blade retainers 9 are subjected to radial displacementto vary-the'diameter-of the propeller blades.

-The pressure of the actuating fluid is boosted by small plunger'pumps l8 which areactuated by a cam !9- which will be hereinafterexplained in' greater detail;

A: check valve 2!! permits the oil to fi'ow into the blade displacement system but prevents its return, thereby maintaining the pressure. The routingof the oil from the booster pumps I8: is controlled by a sleeve or spool valve'li l', the position of which is determined by the pilot setting the controls so that the cam that actuates the valve BI is in proper position. This will alsobe hereinafter described in greater detail.

1 out through duct 29 and annular to the reservoir through drain 29b.

Valve 2i is held against the cam :bycoil spring 22, preloaded by the nut 23, which is designed with a two-wa check valve 24 that serves to replenish the oil system, the oil entering the pump system by valve 25 and duct 26. under pressure is delivered through duct 21 to the spool valve chamber 28, from which it is routed through either th duct 29 to the chamber beneath the piston or the duct 30 shown in dotted lines leading to the fluid chamber above the piston. A control rod 3| for the valve 2! i biased by a'coil spring 32 against the face of a cam 3.!

and is provided with a series of threads 3211 which engage the gear teeth 33 on the lug, rod 34.

The entire assembly is held in place bya ring 41 which is a part of the nose of the engine, the motor shaft 3'being shown in cross-section. V The outside casing 42 (Fig. 3), which actuates cams l9 and 39 is controlled by solenoids 43 and 44 whichinay be energized bya remote control such as a switch (not shown) in the pilots cabin.

of the blades to maintain concentricity of the propeller about the aXis of'rotation.

The operation of the mechanism 'for adjusting the diameter of the blades will now be described.

Starting with the minimum diameter of blade, as'shown'in Fig. 1, when the pilot reaches an altitude where an increased blade diameter is beneficial, or in other words, where it is desired i :to increase the area of the thrust of the propeller, he adjusts his control in the cabin to energize solenoid 44 which moves arm 41 of the cam toward the left, as indicated by the arrow in Fig. 3. This causes cam 39 to displace the control rod 3|, which through its engagement with the lug rod 34 causes'lug 35 to displace valve. 2!.

Cam l9, which is a bevel cam; is subject to axial movement by engagement of its inclined slot 38a with pins 38 to contact the pump plunger l8. Oil at high pressure is forced through the valve 20 and through duct 21 into the. annular duct 28.

' 3 From this duct it is'distributed through duct 30 to the upper piston chamber, and the fluid pressure exerted forces the blade retainer l radially outward carrying the blades with it, thereby increasing the diameter of the blades.

Oil in the fluid chamber below the piston drains chamber 29a When decreased blade diameter is desired, solenoid 44 is energized to move arm 41 to the right in the direction of the arrow. The pump cam I9 is thereb moved through neutral and i into contact with the pumps l8. 1 forced forward causin valve 2| to move in the Valve 39 is reverse direction. High pressure oil enters through ducts 21 and the annular duct 28 and then through duct 29 to the fluid chamber below is the pistons, thereby forcing the blade retainer l0 radially inward to decrease the diameter of t Consequenti ly,.any motion of one blade is duplicated in all 1 The 7 lug 35 of rod 34 engages the sleeve valve 2| by the slot 36.' The cam arrangement is shown in cross-section in Fig. 3 of the drawings in which the outer casing 31 is provided with two pins 33 g which are slidable in the slots of a stationary ring 1 4| and engage the slots of the cams l9 and 39.

through a planetary gear 59.

blades. Fluid from the upper piston chamber is returned to drain through the duct 30.

The pitch setting mechanism will now be de: scribed.

The numeral 53 generally designates the hydraulic actuator which consists of stationary vanes 54 and movabl vanes 55 that are angularly displaceable by fluid pressure routed through the governor valve 2 through passages 56 and 5?, Fig. 1. The movable. vanes. 55 are provided with a ring gear 58 that actuates the master gear 6 The routing of the fluid to the hydraulic actuator will be described in connection with Figs/7 to 9 of the drawings.

As shown in Figs. 1 and '7, th governor housing 2 is mounted on the nose of the engine and is provided with a spline connection 60 through which'it is driven by the engine. The spline B3 is mounted on or integrally formed with a sleeve shaft 6! on which is mounted a hub cap 62 carrying flyweights 63. The flyweights are provided with lever arms 64 that engage the end of a sleeve valve 65 which is preloaded by a coil spring 66 to maintain a neutral position for normal operating speed of the engine. i

The load of spring 66 may be adjusted by a selector mechanism 61 which engages the rack teeth of a sleeve 68 for compressing or extending the coil spring 66 as shown in Fig, 7.

Included with the governor housing 2 is a pump housing 69 containing pump gears 10 and H which deliver fluid from port 12 to a high pressure port 13. A check valve 'M'maintains predetermined pressure of the fluid which is caused to recirculate if the valve is lifted by the fluid pressure. Valve passages and 16 are connected to the hydraulic actuator, as shown diagrammatically in Figs. 8 and 9, and the pressure fluid from passage 13 is routed to the actuator in accordance with the movement of the governor valve 655 to either advance or retard the pitch setting.

Return fluid flows from passage 1! to theene gine sump or to the storage space. The numeral 69a designates an engine driven pump for circulating lubricating fluid through the engine, the pumpbeing connected on one side of the hy-, draulicactuator 53 to maintain a constant low pressure fluid on one side of the movable vanes' 55 which is overcome by the pressure fluid of booster pump 69 to effect high pitch setting. A hydraulic motor driven pump 6% i connected to the governor valve passage 73 as shown and is electrically driven for feathering and unfeathering the blade if the engine driven pump 69 and 69a fail as when the engine stops. The electrically driven pump 69b is connected in an electrical power circuit having terminal contacts '19 and 80, Fig. 10, cooperating with control lever 78.

The governor valve 65 can be operated independently of the action of the flyweights 63 through the selector mechanism 61 which is ac tuated by a control lever 18, Fig. 10, operating between the stops 19, 19a, 80, a, the control range of lever 18 through the range designated B being the normal control range for constant speed, range A the feathering control range, and range C the unfeathering range.

In thisrnanner the hydraulic actuator can be operated independently of the engine speed.

In Fig. 5, the design of the variable diameter mechanism and the pitch setting mechanism are modified to be coordinated by the governor valve mechanism 2 with electric contacts such as the contacts I23 and I24, Fig. 11 that energize the solenoids 43 and 44, to effect the proper setting a of the cam mechanism. In Fig; the 2 end gears Toff the blade ferrules coact with a: master-gear; B I that' islocked 'to-the: actuator housi'n'gtfi which revolves'with the'irotor 832-. The housing 82'ispro4 vided Withan end bearing 8min the .hub housing. and the ballrace ifil The coordinating; ring 8 3i is connected to the-actuator-housing 52 by bolts 86a; and has-* arms 85! which engage the rings 88 of jthe bladeretainers-a to-be actuated by rotation of housing 82- to coordinate radial"move-- ment of the blades in accordance withtheinovement of-the=hydraul'ic actuator 83.

The pressure fluid is self contained in the space of thehub unit andis supplied through the valve passage-24 to the valve 21 from which it is de livered'through the valve passage'25 to the booster pump- I8; Thehigh pressure fl'uid is then delivered through passage 21- to the; high pressure port 28 of the valve 2i from which his routed through glands tfi'and to the fluid'chambers above crbelo'w the piston M as directed by the position of valve 2! by cam 39; Fig. 3; When the high pressure fluid is connected to the gland 3 3 for displacing the blade retainer 9 radially outward to increase the diameter of the-propeller, it is simultaneously connected to the gland 5% of the pitch setting actuator to effect pitchad'- justment of the'blade, and when the valve 2-1 is moved to deliver the highpressure-fluid through gland 29' to displace the bladeretainer Sradi'all'y inwardly, glands 30 and-53 are-connectedt'o-drain and the hydraulicpitch adjusting mechanism is displaced toits normal position by the centrifugal thrust on the blade. In this manner both the propeller diameter and" pitch adjustment are coordinated through the governor control valve 2, hereinafter'described in connection with Fig; 3.1 of the drawings.

Thedesign of Fig. 5 would be operative to simultaneously adjust the diameter andpitchof the propeller through the coordinating mechanism Bl and 8-8 connectedto the bracket 8% which is; rotatable With the hydraulic actuator irrespective of the manner of application of the pressure fluid. Thus, for example; if the fluid wereapplied only to'the fluid" chambers of' the piston l4 radial movement of the blade retainer 9 would effect rotation of the pitch adjusting mechanism independently of any application of pressure fluid to the latter, and similarlyg'ir the pressure fluid were applied only to the' pitchadjusting actuator-to rotate its housing 8-2 thedi: ameter of the propellenwould simultaneously-be adjusted through the coordinatinglinkage 8? independently'of any'pressure' fluid application" to the fluid chambers above or belowthe piston it. However, by the application: of t-h-epres'siue fluid to both the diameter an'dpitch adjusting actuators a more efiicient and balanced adjustment of these'parts is obtained.

Still another modification of thedesign in which the variable diameter and'pitch setting mechanisms are coordinated is shown in-Fi'g; 6.

The hydraulic propeller unit comprises a hub fitrthat is mounted on an engineshaft' 91' which has a two-way oil gland designated by numerals 92 and 93. The hub 90. is of the split design. The blade root is designatedby 'thenumeral 95; The spider eeis splined on shaft iilto rotate there'- with as shown at-Sl; The outward andinward radial movement of the blade 95*is accomplished by rotation of the" gear sleeve fitfwhich has' an end gear 59; the sleeve gear 93* being mounted on a stack bearing I90. Rotation: of the blade 95 on its own axis isprevented by an antifriction splih consisting: ofballs I 01 in slotsd 02;

which are angularly disposedaround thebladej J The sleeve ge'ar S3' is rotated bya gear I09 thati'ispowered' through a hollow sleeve l-I'Dby a torquaunit" M I which is actuatedbythe application .ofpressur fiuid through" glands llld andtiliti 6 controlled by a manually-operated valve (not show-n0 r The threads H2 of the bladeretainer and of the sleeve gear es 'are ground to receive ball bearings ll3' and the'helix angle of the'bearing threads H 2 is such that the centrifugal force of theblades tendsto turn the blades to high pitch, thereby balancing-out the centrifugal twisting moment, tending towards low-pitch.- This reduces theforce required to change the blade-angle:

It will be noted that by operation of the pitchsetting actuator 1%; the blade sdis rotated for pitch setting as determined' by the hydraulic governor velvet, and by operation of thefluid pressure unit Ml}, gear It?! and gear sleeve 98 are-rotated; which causes the blade 55 to move radially inwardor out, as'the case maybe;

In Fig. 11, the governor valve' B5- is shown coordinated' with the solenoid-actuated cam mechanism of Fig. 3-through"a'servomotor H5. The servomotor consists of cylinder connected by conduit Htto the fluid pressure system of the governor valvefii: for the delivery of. fluid under pressure to actuate piston i II in response to variations-in speed aseifecting the operation of the flywei'ght' 63 on the valve 65'. Piston Il'l'actuates an electrical contact H8 connected to a source'of electrical energy, designated by the, numeral l*l'9:.

The solenoidsv 43 and 4'4 ofFig. 3 are. shown electrically connected in the circuit l2!) andby conductors l2! and I22 to electricalcontacts lm and IE4. If the piston- H! which is maintained in a neutral. position by coil spring I25 effects contact ofthe terminal H3 with. terminal I23"; the solenoid 455' will be energized; and if terminal H8 contacts solenoid I24, solenoid 44 will be energized to control thecam mechanisms in response to the engine speed. To prevent abrupt adjustments by contact of. the movable terminal I i'8with the terminals I23 and 124;.the latter are mounted on a reciprocating rod I26 having a. roller I21 riding on cam I28. The cam is actuated by gear wheels 5'29 and [30, the latter being mounted on the end. of ashaft I31 that is geared through a gear wheel] i32..to a rack I33 attached to thegovernorvalve. g

If thegovernor valve is subjected to fluctuations by movement of the governor weights. 63' becauseof variationsofthe engine-speed, the'rod 126:. will be similarly; subjected: to fluctuating movements: with: the result that contacts: 1 23 and 524 will be subject to slight reciprocato-rymovementlwithoutnecessarily engaging contact I I8;

It requires but avery little m'ovement" of the 'valveto'open thepor't to the fluid'pressure line H6 of the servomotor so that fluctuating move"- ments' of the contacts i2 3 and 124 are not enough to prevent contact of the terminal-' I I8 'when' the servo piston pressure of the system.

' The numeral I35 diagrammatically illustrates the source of pressure fluid such as a pump with a check valve I36, permitting recirculation of the fluid atpredetermined pressures.

The mechanism shown in Fig. 11 coordinates the diameter increasing movement ofthe blades with the pitch adjusting actuator if it is desired to have both functioning simultaneously in response to speed variations of the engine. a It is evident from the foregoing description of the invention that the propeller thrust may be varied by either increasing the diameter of the blades or by adjusting the pitch setting or both.

, The advantages of this type of propeller appear toadapt it especially to motors of from 4,000 to 6,000 horsepower. In the take-off the pilot independently control the diameter of the blades entirely separate from the constant speed control by contracting them to minimum diameter to deliver maximum horsepower. maybe set at their maximum diameter with a relatively fiat pitch, and after levelling off they may be contracted for cruising only, on' the constant speed pitch-setting unit, and perhaps after climbing to 30,000 feet it would again be desirable to use the maximum diameter blade, together 7 with the constant speed pitch control, not advariced to its position for a maximum pitch angle.

In taking off to. get the maximum horsepower, it would bedesirable to take off load by drawing inthe diameter of the blades, and on the take- ,off and climb the'constant speed pitch-setting mechanism would permit the blades to deliver When at sea level at atmaximum horsepower. mospheric pressure, the pitch of the propeller operating at constant speed would be rather fiat withv a minimum diameter blade, and as the higher levels of 10,000 to 20,000 feet are reached,

the constant speed pitch would be nearing its maximum increased pitch setting. .The pilot would then make use of a greater diameter blade. As the diameter is increased, the pitch control would flatten out again so that the useful range of pitch adjustment for constant speed would again be available.

It is evidentfrom the foregoing description of the invention that various modifications may be made in the details of construction without departing from the principles herein set forth.

I claim:

1. In a propeller mechanism, a hub structure, a plurality of propeller blades mounted for radial and angular movement in said hub, an actuator for moving the blades radially of the hub to vary the propeller diameter, an actuator for subjecting the blades to angular movement about their longitudinal axis independently of said blade movingmeans, and'control means for coordinating said actuators to be simultaneously operable.

2. In a variable thrust propeller mechanism, a hub structure, a plurality of propeller blades mounted for radial and. angular movement in said'hub structure, an actuator for varying the diameter of the propeller blades, a second actuator operable independently of said first-named actuator for varying the pitch of said blades, control means to selectively energize said actuators including means for coordinating the movements of said actuators in their thrust adjusting func-,

tion.

3. In a variable thrust propeller mechanism,

a hub structure, a plurality of propeller blades is subjected to the fluid W111 probably wish to The blades 7 pressure means for varying the pitch of the pro peller blades, and means responsive to theprorespective fluid pressure means.

peller speed for simultaneously energizing/the 4. In a. variable thrust propellermechanism, a v V hub structure, a plurality of propeller blades mounted for radial and angular movement in said hub structure, hydraulic actuating means for varying the pitch of the propellerblades, fluid pressure means for varying the diameter of the propeller blades, cam mechanism controlling the application of the respective fluid pressure means, a governor valve controlling the application of fluid to said hydraulic actuator, and means responsive to movement of the, governor valve for controlling said cam mechanism.

5. In a variable diameter propeller unit, a hub having a plurality of radial arms with pistonsat the ends thereof, blade retainer sleeves'mounted for axial movement in said hub having cylinders for receiving the pistons of the hub, fluid pressure means including flow glands extendingthrough said radial arms and pistons for actuating said cylinders, valve means controlling the application of said fluid pressure means above and below said piston to selectively displace the blade retainersleeves relative to said pistons, and con-. necting rods secured'to the blade retainer sleeve and to a coordinating ring whereby the movement of the blade retainer sleeves is coordinated.

6. A variable diameter propeller unit comprising a hub having radial arms with piston heads and having integrally formed sleeve portions coextensive with said arms, blade retainer sleeves disposed between said hub retaining sleeves and piston elementshaving cylinders coacting with the pistons of the hub, fluid pressure means including flow glands extending through said ra dial arms and pistons for actuating said cylinders, valve means directing the application of said fluidpressure means above or below the piston elements to correspondingly displace the blade retainer sleeves, cam mechanism controlling the movement of said valve and control means for actuating said cam mechanism.

'7. A variable diameter propeller hub unit comprising a hub having radial arms terminating in piston heads and having integrally formed sleeves coextensive with said arms and piston heads, blade retainer sleeves disposed between saidhub sleeve and pistons and having cylinders coacting with said hub pistons, fluid flow passages for directing fluid under pressure above and below said pistons, plunger pumps for delivering fluid under pressure, a valve controlling the direction of flow of the fluid above and below the pistons, cam mechanism for actuating said plunger pumps and valve, and control means for setting the cams in the path of movement of the pump plungers and valve actuating members, connecting rods for said blade retainer sleeves and a coordinating ring joined to said connecting rods whereby the movement of all of the blades is coordinated.

8. In combination, a variable diameter and varject the blade retainer sleeves to angular movement, fluid pressure means including flow glands extending through said radial arms and pistons, a valve for directing fluid above and below the pistons to subject the blade retainer sleeves to movement radially oi the hub, and control means for setting said valve to selectively increase or decrease the diameter of the blades.

9. In combination, a variable pitch and variable diameter propeller mechanism con1prising a hub structure, piston elements mounted on said hub structure, blade sleeves having cylinders coacting with said pistons, blade ferrules having end gears disposed around said blade retainer sleeves having angularly spaced slots in alignment with complemerh tary slots of said blade retainer sleeve, ball bearings disposed in said slots to permit relativeiy axial movement of said blade retainer sleeves and ferrules, a master gear coacting with the end gears of said ferrules;'a hydraulic actuator for said master gear, a governor control for energizing said hydraulic actuator in response to a variation. in the engine speed to vary the pitch setting of the propeller blades, and fluid pressure means including a valve and cam control mech-- anism for directing fluid under pressure above or below the hub pistons to subject the blade retainer sleeves to radial movement relative to the hub.

10. In combination, a variable diameter and variable pitch propeller mechanism comprising a hub having a plurality of blade retainer sleeves mounted for radial movement therein, blade ferrules enveloping said blade retainer sleeves mounted to be rotatable therewith and hired against radial movement, said ferrules having end gears, a master gear engaging said end gears, an actuator for said master gear, coordinating mechanism connecting said actuator and blade retainer sleeves, means for subjecting the blade retainer sleeves to radial movement and for simultaneously actuating the blade ferrules to subject the blade retainer sleeves to angular move ment whereby to simultaneously adjust the blade diameter and pitch setting of the blades.

11. In combination, a variable diameter and variable pitch propeller mechanism comprising a hub structure including a spider, the arms of which are provided with stack bearings for journalling a gear sleeve having helical grooves on retainer the outer periphery thereof, blade retainer sleeves tainer sleeve and, having ball races disposed in said slots to permit relative axial movement of said blade retainer sleeve and gear sleeve, a hydraulic actuator having a master gear for engaging the teeth of said external gear sleeve and a hydraulic actuator having a master gear for engaging the teeth of said internal gear sleeve, and means for energizing said actuators whereby the blade retainer sleeves are subjected to an- I gular movement to vary their pitch setting and to movement radially of the hub to vary the blade diameter.

112. In a variable thrust propeller mechanism, a hub structure, propeller blades mounted thereinfpitch adjusting mechanism for said blades including an hydraulic actuator, fluid pressure means for changing the diameter of. said blades, pump mechanism for delivering fluid under pressure to said diameter changing means, valve means controlling the flow of fluid pressure from said, pump mechanism, cam mechanism for actuating said pump and valve, and governor control means operative in response to the speed of the propeller for controlling said cam mechanism to regulate the pitch adjusting mechanism and for routing pressure fluid to said hydraulic actuator.

13. In a variable thrust propeller mechanism, a hub structure having blades mounted therein,

' a hydraulic actuator for varying the thrust of said blades, pump mechanism and valve means for delivering fluid ressure to said actuator, said pump and valve mechanism being mounted in the hub, cam mechanism for actuating said pump in response to rotary movement of the hub, means for regulating said cam mechanism to regulate the pump and valve mechanism comprising solenoids for actuating said cam, an electrical power circuit for energizing said solenoids including a movable contact, a servo motor for operating said contact and a governor control mechanism for energizing said servo motor.

WALTER S. HOOVER. 

